linux-kernel - Re: KASAN: null-ptr-deref Write in get

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Date:   Mon, 23 Mar 2020 20:18:03 +0800
From:   Qiujun Huang <anenbupt@...il.com>
To:     Dan Carpenter <dan.carpenter@...cle.com>
Cc:     syzbot <syzbot+4a88b2b9dc280f47baf4@...kaller.appspotmail.com>,
        aeb@....nl, danarag@...il.com, kstewart@...uxfoundation.org,
        linux-kernel@...r.kernel.org, syzkaller-bugs@...glegroups.com,
        tglx@...utronix.de, viro@...iv.linux.org.uk,
        Qiujun Huang <hqjagain@...il.com>
Subject: Re: KASAN: null-ptr-deref Write in get_block

On Mon, Mar 23, 2020 at 7:42 PM Dan Carpenter <dan.carpenter@...cle.com> wrote:
>
> Fix the subject to [PATCH] minix: Fix NULL dereference in alloc_branch()
>
> On Sun, Mar 22, 2020 at 08:06:48PM +0800, Qiujun Huang wrote:
> > Need to check the return value of sb_getblk.
> >
>
> Add a Reported-by tag.
>
> Reported-by: syzbot+4a88b2b9dc280f47baf4@...kaller.appspotmail.com
>
> > Signed-off-by: Qiujun Huang <hqjagain@...il.com>
> > ---
> >  fs/minix/itree_common.c | 2 ++
> >  1 file changed, 2 insertions(+)
> >
> > diff --git a/fs/minix/itree_common.c b/fs/minix/itree_common.c
> > index 043c3fd..eedd79f 100644
> > --- a/fs/minix/itree_common.c
> > +++ b/fs/minix/itree_common.c
> > @@ -85,6 +85,8 @@ static int alloc_branch(struct inode *inode,
> >   break;
> >   branch[n].key = cpu_to_block(nr);
> >   bh = sb_getblk(inode->i_sb, parent);
> > + if (!bh)
> > + break;
>
> The patch is white space damaged and we need to do a bit of error
> handling before the break as well.

I get it, thanks.

>
>         bh = sb_getblk(inode->i_sb, parent);
> +       if (!bh) {
> +               minix_free_block(inode, block_to_cpu(branch[n].key));
> +               break;
> +       }
>         lock_buffer(bh);
>
> Please fix those few things and resend.
>
> regards,
> dan carpenter
>